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PubMed1999

Responses of three species of adult ticks (Acari: Ixodidae) to chemicals in the coats of principal and minor hosts.

In laboratory bioassays, host-seeking adult blacklegged ticks, Ixodes scapularis Say, lone star ticks, Amblyomma americanum (L.), and American dog ticks, Dermacentor variabilis (Say), were exposed to substances from the pelage of dogs and white-tailed deer, Odocoileus virginianus (Zimmermann). Male A. americanum exhibited an arrestant response to all samples of deer tarsal gland substances tested, whereas female A. americanum, female I. scapularis, and male and female D. variabilis responded to samples from certain deer and not others. Female I. scapularis, D. variabilis, and A. americanum of both sexes also showed an arrestant response to substances rubbed from the dorsal surface of dogs' ears. These findings suggest that, although these 3 species of ticks are associated with certain host species as adults (A. americanum and I. scapularis with white-tailed deer, D. variabilis with dogs), their repertoires of host-finding behaviors are broad, and use of minor host species may not be purely accidental.

Animals↗
PubMed2001

Selective ablation of antennular sensilla on the Caribbean spiny lobster Panulirus argus suggests that dual antennular chemosensory pathways mediate odorant activation of searching and localization of food.

In spiny lobsters and other decapod crustaceans, odorant-mediated searching behavior patterns are driven primarily by chemosensory neurons in the antennules. Two groups of antennular chemosensory neurons can be distinguished on the basis of the sensilla that they innervate and their central projections: those that innervate the aesthetasc sensilla on the lateral flagella and project into the glomerularly organized olfactory lobes, and those that innervate other (i.e. non-aesthetasc) sensilla on both lateral and medial flagella and project into the stratified and non-glomerularly organized lateral antennular neuropils. By ablating different groups of antennular sensory neurons or sensilla, we examined the role of aesthetasc and non-aesthetasc chemosensory neurons in regulating local searching behavior of Caribbean spiny lobsters, Panulirus argus, for food (squid) in a low-flow environment. The results show that odorant-mediated activation of searching and localization of food under these conditions requires only a subset of functional antennular chemosensory neurons, since neither aesthetasc chemosensory neurons nor non-aesthetasc chemosensory neurons are by themselves necessary for these types of behavior. However, ablation of aesthetasc chemosensory neurons together with subsets of non-aesthetasc chemosensory neurons from either the medial or lateral flagella impairs the ability of lobsters to locate the food. This reveals a large degree of functional redundancy but also some complementary functions between aesthetasc and non-aesthetasc chemosensory neurons, and hence between these dual antennular chemosensory pathways, in odorant-mediated searching behavior of lobsters under these conditions.

Animals↗
PubMed1991

Distinguishing between haloperidol's and decamethonium's disruptive effects on operant behavior in rats: use of measurements that complement response rate.

The behavioral effects of haloperidol (0.04 to 0.16 mg/kg) and nonparalytic doses of decamethonium (0.2 to 0.8 mg/kg) were studied with operant methods that permitted the measurement of response rate, peak force of response, duration of response, and duration of the rat's head entry into the reinforcement dipper well. Type of operant response topography (forelimb press or forelimb grasp-and-pull) and peak force (low or high) required for reinforcement delivery were independent variables. The low-force, press-topography condition yielded qualitatively different profiles for the two drugs. Haloperidol increased peak force and duration of operant response, increased maximum head entry duration, and temporally dissociated forelimb and head entry behavior. Decamethonium decreased force and duration of operant response, did not appreciably affect maximum head entry duration, and did not influence the normal temporal coupling of forelimb and head entry responses. The haloperidol effects were seen as reflections of pseudo-Parkinsonism, not muscle weakness, which appeared to be the primary source of decamethonium's behavioral effects.

Animals↗
PubMed2006

Disruption of responding maintained by conditioned reinforcement: alterations in response-conditioned-reinforcer relations.

An observing procedure was used to investigate the effects of alterations in response-conditioned-reinforcer relations on observing. Pigeons responded to produce schedule-correlated stimuli paired with the availability of food or extinction. The contingency between observing responses and conditioned reinforcement was altered in three experiments. In Experiment 1, after a contingency was established in baseline between the observing response and conditioned reinforcement, it was removed and the schedule-correlated stimuli were presented independently of responding according to a variable-time schedule. The variable-time schedule was constructed such that the rate of stimulus presentations was yoked from baseline. The removal of the observing contingency reliably reduced rates of observing. In Experiment 2, resetting delays to conditioned reinforcement were imposed between observing responses and the schedule-correlated stimuli they produced. Delay values of 0, 0.5, 1, 5, and 10 s were examined. Rates of observing varied inversely as a function of delay value. In Experiment 3, signaled and unsignaled resetting delays between observing responses and schedule-correlated stimuli were compared. Baseline rates of observing were decreased less by signaled delays than by unsignaled delays. Disruptions in response-conditioned-reinforcer relations produce similar behavioral effects to those found with primary reinforcement.

Animals↗
PubMed1984

A comparison of prey eating by spontaneous mouse killing rats and rats with lateral septal, medial accumbens, or medial hypothalamic lesions.

Rats with lesions of the medial hypothalamus and spontaneous mouse killing rats were tested for mouse and rat pup killing in their living cages 1 and 3 days postoperatively. The lesioned and spontaneous killers did not differ significantly in amount of prey eaten within 10 min following a mouse kill on either Day 1 or 3 postoperatively. Both groups ate significantly more of the prey than did sham-lesioned rats that were presented with a freshly killed mouse. When 4 hr was allowed for eating following a kill, rats with lesions of the lateral septum, medial accumbens, and medial hypothalamus each ate significantly more than spontaneous mouse killing rats. The greater prey eating by the lesioned animals is probably not the result of the prey being a highly palatable food since rats with medial hypothalamic lesions but not those with medial accumbens or septal lesions showed enhanced consumption of a sweetened lab chow over a 4 hr period. The quantitative similarity in the prey eating by spontaneous and lesion-induced mouse killers in the period immediately following the kill serves to further establish a relationship between these two kinds of killing. The greater eating that occurs in lesioned animals when a longer time is allowed for eating is consistent with other observations of excesses in the killing behavior of lesioned animals relative to spontaneous killers.

Animals↗
PubMed1990

Dynamics of plasma catecholamine and corticosterone concentrations during reinforced and extinguished operant behavior in rats.

Plasma noradrenaline (NA), adrenaline (A) and corticosterone (CS) concentrations were determined simultaneously in permanently heart-cannulated rats before and during the performance of reinforced and nonreinforced (extinguished) operant behavior. Shortly before the experimental food-reinforced (VI 15-sec schedule) lever-pressing task, anticipatory elevations of plasma NA and CS contents were observed. During reinforced lever responding plasma NA increased, A did not change and CS declined. Extinction was associated with a transient increase in A, decreasing NA and elevated CS concentrations. In addition, a relationship was found between individual lever-pressing rate, neurosympathetic and adrenomedullary reactivity and the degree of schedule-induced polydipsia. The results indicate that presence and absence of expected behavioral consequences (controllability and loss of control, respectively) are attended by selective, but highly dissociated patterns of neurosympathetic, adrenomedullary and adrenocortical output. Collectively, the findings reinforce the concept that distinctive emotional and/or motivational states are associated with different patterns of neuroendocrine responses. The reactivity of the sympathoadrenomedullary component is heavily dependent upon a rat's individual behavioral strategy.

Adrenal Medulla↗
PubMed1993

Failure of a tryptophan-free amino acid mixture to modify sexual behavior in the female rat.

Female Wistar rats, weekly injected with estradiol valerate after ovariectomy, were trained to cause a sexual contact with a potent male by operating a lever. Contact-response latencies, which vary according to the nature of the sexual contact, were measured as an index of the female's sexual motivation. In these experimental conditions the administration of a tryptophan-free amino acid mixture, which has been proved to decrease brain serotonin and to enhance male mounting behavior, failed to modify the sexual motivation of the female rats.

Amino Acids↗
PubMed1994

Effects of trimethyltin on acquisition and reversal of a light-dark discrimination by rats.

The behavioral deficits produced by trimethyltin (TMT) are usually attributed to the hippocampal damage caused by this toxicant. The purpose of this experiment was to determine the effects of TMT administration on acquisition and reversal of a discrete trial light-dark discrimination. Acquisition of this task is impaired by hippocampal lesions but the effects of TMT on it are not known. Forty-five days after some of the rats were given one of three doses of TMT, adult, male Long-Evans rats were given 100 trials per day for 20 days to acquire a discrete trial lever press discrimination with lit cue lights located above the correct lever. At the end of this time the contingencies were reversed and the rats were given 30 more days of training. No significant group differences occurred during the first 20 days. A significant group effect was found for the 30 days of reversal training. The rats given the highest dose of TMT (6 mg/kg) obtained significantly more reinforcements during reversal training than the other groups. Because surgical hippocampal lesions generally impair both acquisition and reversal of visual discriminations, these data were unexpected and suggest that other factors than hippocampal damage enter into the behavioral effects of TMT.

Animals↗
PubMed1985

Effects of post-trial injection of beta-endorphin on shock-induced fighting are dependent on baseline of fighting.

The effects of repeated post-trial administration of 10 micrograms/kg beta-endorphin on the development of mutual fighting in pairs of rats submitted to various intensities of electric shock were investigated. beta-Endorphin blocked the development of fighting responses when a low footshock intensity was used, but facilitated it when a high shock intensity was delivered. A detailed analysis of the relationship between shock intensity, baseline of fighting, and effects of beta-endorphin showed that the effects of beta-endorphin were dependent on the behavioral baseline rather than on shock intensity per se.

Animals↗
PubMed1985

Dorsomedial diencephalic involvement in the juvenile play of rats.

Lesions of either the dorsomedial thalamus (DMT) or the parafascicular region of the thalamus (PFA) reduced rough-and-tumble social play in juvenile rats, as measured by frequency of pinning. Pinning was reduced by 33% in pups with DMT lesions and by 73% in pups with PFA lesions. Although PFA lesions had minimal effects on average pin durations, DMT pups had pins that were, on average, 105% longer than those of controls. Lesions of the PFA, but not DMT, also reduced play solicitation behaviors. Pups with PFA lesions were also insensitive to the play modulating effects of both naloxone and morphine. DMT pups were sensitive to the facilitatory effects of morphine, but naloxone was without effect in these animals. Control studies designed to evaluate general behavioral competence showed that the observed lesion effects were relatively specific to play.

Animals↗
PubMedDate not supplied

Firing characteristics of deep layer neurons in prefrontal cortex in rats performing spatial working memory tasks.

Single cells were recorded with 'tetrodes' in regions of the rat medial prefrontal cortex, including those which are targets of hippocampal afferents, while rats were performing three different behavioral tasks: (i) an eight-arm radial maze, spatial working memory task, (ii) a figure-eight track, delayed spatial alternation task, and (iii) a random food search task in a square chamber. Among 187 recorded units, very few exhibited any evidence of place-specific firing on any of the behavioral tasks, except to the extent that different spatial locations were related to distinct phases of the task. Furthermore, no prefrontal unit showed unambiguous spatially dependent delay activity that might mediate working memory for spatial locations. Rather, the cells exhibited diverse correlates that were generally associated with the behavioral requirements of performing the task. This included firing related to intertrial intervals, onset or end of trials, selection of specific arms on the eight-arm radial maze, delay periods, approach to or departure from goals, and selection of paths on the figure-eight track. Although a small number of cells showed similar behavioral correlates across tasks, the majority of cells showed no consistent correlate when recorded across multiple tasks. Furthermore, some units did not exhibit altered firing patterns in any of the three tasks, while others showed changes in firing that were not consistently related to specific behaviors or task components. These results are in agreement with previous lesion and behavioral studies in rats that suggest a prefrontal cortical role in encoding 'rules' (i.e. structural features) or behavioral sequences within a task but not in encoding allocentric spatial information. Given that the hippocampal projection to this cortical region is capable of undergoing LTP, our data lead to the hypothesis that the role of this projection is not to impose spatial representations upon prefrontal activity, but to provide a mechanism for learning the spatial context in which particular behaviors are appropriate.

Action Potentials↗
PubMed2003

Odor localization requires visual feedback during free flight in Drosophila melanogaster.

Adult fruit flies follow attractive odors associated with food and oviposition sites through widely varied visual landscapes. To examine the interaction between olfactory and visual cues during search behavior, we recorded three-dimensional flight trajectories as individuals explored controlled sensory landscapes. When presented with the source of an attractive odor invisibly embedded in the floor of a 1 m arena, flies spend most of their time hovering back and forth over the source when flying within a randomly textured visual background but fail to localize the source when searching within a uniform white surround. To test whether flies are associating unique features of the visual background with the strength of odor cues, we flew them within arenas containing evenly spaced vertical stripes. Flies readily localized the odor when flying within visual landscapes lacking azimuthal landmarks provided that vertical edges were present. Flies failed to localize odor when flying within a background pattern consisting of horizontal stripes. These results suggest that, whereas flies do not require spatially unique visual patterns to localize an odor source, they do require visual feedback generated by vertical edges. Quantitative shifts in several components of flight behavior accompanied successful odor localization. Flies decrease flight altitude, turn more often and approach visually textured walls of the arena near an odor source. A simple model based on the statistics of flight behavior supports the hypothesis that a subtle influence on these behaviors is sufficient to lead a fly to its food.

Animals↗
PubMed1993

DRL interresponse-time distributions: quantification by peak deviation analysis.

Peak deviation analysis is a quantitative technique for characterizing interresponse-time distributions that result from training on differential-reinforcement-of-low-rate schedules of reinforcement. It compares each rat's obtained interresponse-time distribution to the corresponding negative exponential distribution that would have occurred if the rat had emitted the same number of responses randomly in time, at the same rate. The comparison of the obtained distributions with corresponding negative exponential distributions provides the basis for computing three standardized metrics (burst ratio, peak location, and peak area) that quantitatively characterize the profile of the obtained interresponse-time distributions. In Experiment 1 peak deviation analysis quantitatively described the difference between the interresponse-time distributions of rats trained on variable-interval 300-s and differential-reinforcement-of-low-rate 72-s schedules of reinforcement. In Experiment 2 peak deviation analysis differentiated between the effects of the psychomotor stimulant d-amphetamine, the anxiolytic compound chlordiazepoxide, and the antidepressant desipramine. The results suggest that peak deviation analysis of interresponse-time distributions may provide a useful behavioral assay system for characterizing the effects of drugs.

Animals↗
PubMed1979

Alimentary instrumental responses and neurological reflexes in amygdalar cats.

Lesions in ventromedial part of amygdala impaired neither alimentary instrumental reflexes nor food intake, but impaired predatory behavior. Lesions localized in the more dorsal and lateral part of the amygdala produced disorders in instrumental performance and food intake without changes in predatory attack. Both kind of lesions did not impair neurological reflexes, therefore the abolishment of predatory attack after ventromedial amygdala damage was not caused by sensory-motor disturbances. It is concluded that predatory behavior is based on specific mechanisms separate from both alimentary and instrumental ones.

Amygdala↗
PubMed1999

p-Chloroamphetamine (PCA) suppresses ingestive behavior in male rats.

Ingestive behavior was activated in male rats by intraoral intake and intake from a bottle of 1-M solution of sucrose. Intraperitoneal injection of p-chloroamphetamine (PCA), releasing central 5-hydroxytryptamine (5-HT) from serotonergic nerve terminals, inhibited ingestion of the sucrose solution. Significant inhibition of sucrose intake by PCA was observed at 1.25 and 2.5 mg/kg dose in a bottle intake test, and at 5.0 mg/kg dose in an intraoral intake test. These findings suggested that 1.25 and 5.0 mg/kg of PCA suppressed appetitive ingestive behavior and consummatory ingestive behavior in male rats, respectively.

Administration, Oral↗
PubMed2001

Effect of neonatal dentate gyrus lesion on allothetic and idiothetic navigation in rats.

Goal-directed navigation is believed to be the combined product of idiothetic and allothetic orientation. Although both navigation systems require the hippocampal formation, it is probable that different circuits implement them. Examination of Long-Evans rats with dentate gyrus lesions induced by neonatal X-ray irradiation may show the dissociation of these two components of navigation. Two recently developed place avoidance tasks on a rotating circular arena were used to test this hypothesis. In the first test, the position of the punished area is stable in the room frame but is permanently changing on the surface of the arena. This task requires the rat to use allothetic orientation and to disregard idiothetic orientation. In the second test, the prohibited area is fixed in the coordinate system of the arena and the experiment is conducted in complete darkness, forcing the rat to rely exclusively on idiothesis supported by substratal cues. The results suggest that the dentate gyrus lesion interferes less with idiothetic orientation than with allothetic orientation. In addition, an attempt was made to control the number of developing granule cells by exact timing of a single high dose of perinatal irradiation, and to measure the ensuing behavioral deficits. Rats irradiated at 6, 18, or 24 h after birth were tested as adults in the Morris water maze. Irradiated animals showed significant, but highly variable, learning deficit, but histological examination indicated that the granule cell loss did not correlate with the degree of behavioral impairment.

Animals↗
PubMed2006

Alterations in behavioral flexibility by cannabinoid CB1 receptor agonists and antagonists.

RATIONALE: Cannabinoid CB1 receptors are expressed in the prefrontal cortex, but their role in mediating executive functions such as behavioral flexibility is unclear. OBJECTIVE: The present study examined the effect of pharmacological activation or blockade of the cannabinoid CB1 receptors on behavioral flexibility using a strategy set-shifting task conducted on a cross maze. MATERIALS AND METHODS: In experiment 1, rats initially were trained to turn left or right while ignoring the visual cue to obtain a food; on the second test day, rats had to inhibit the previously learned rule and approach the cue to obtain the food. In experiment 2, the order of discrimination training was reversed. RESULTS: Administration of the cannabinoid CB1 receptor agonist HU-210 before the set-shift on day 2 elicited dose-dependent effects on performance. A 20-microg/kg dose of HU-210 increased perseverative errors, whereas the effects of a lower, 5-microg/kg dose caused differential effects depending on whether rats were required to shift from a response to a visual-cue discrimination strategy or vice versa. Conversely, administration of a 2-mg/kg, but not a 5-mg/kg dose of the CB1 receptor antagonist AM251 reduced perseverative errors. CONCLUSIONS: These data demonstrate a biphasic and dose-sensitive role for the cannabinoid system in behavioral flexibility, which in turn may have clinical implications for the role of the endocannabinoid system in psychiatric disorders where behavioral flexibility is compromised.

Animals↗
PubMed1991

Indices of stress in rats: effects of sex, perinatal alcohol and artificial rearing.

Three groups of rats were normally reared by dams, artificially reared but not exposed to alcohol or artificially reared and exposed to 6.6 g/kg/day of ethanol condensed into 8 h of each 24-h period. Alcohol exposure was given from postnatal day 4 through 9 and artificial rearing was conducted from postnatal day 4 to 12. In adulthood, approximately half of the rats were fitted with a chronic jugular catheter and were exposed to swim stress for 1 min in 21 degrees C water. Alcohol exposure augmented the corticosteroid stress response to the swim stress in female rats but not in male rats. The other half of the animals were tested for acquisition and extinction of a conditioned emotional response (CER). While alcohol exposure had no effects on the CER, extinction of CER was greatly accelerated by artificial rearing alone in female rats but not in male rats. Taken together, these findings suggest that some aspects of the stress response in female rats are more vulnerable to insults during the early postnatal period than those in male rats and that the insult-induced alterations can affect hormonal and behavioral measures differentially.

Adrenal Cortex Hormones↗